Meeting Abstract

S2.3  Tuesday, Jan. 4  Shifts in muscle activity patterns during the evolution of feeding in gnathostomes KONOW, N*; HERREL, A; WILLIAMS, S; ROSS, CF; DE VREE, F; CROMPTON, AW; GERMAN, RZ; SANFORD, CPJ; GINTOF, C; Brown University; CNRS/MNHH; Ohio University; University of Chicago; University of Antwerp; Harvard University; Johns Hopkins University; Hofstra University; Hofstra University nkonow@brown.edu

Shifts in muscle activity patterns (MAP) driving distinct animal movements are rarely reported. This may be because MAPs are labile at shallow phylogenetic levels (among individuals, between species and genera), where most comparisons have been performed, and conserved at deeper levels (comparisons between families or orders) where previous comparative analyses did not focus. Alternately, previous comparisons might not have bracketed major behavioral changes that would require a shift in MAP. Moreover, conventional time-series analyses of EMGs might be insensitive to subtle changes in MAP integration and coordination. Here, we study the evolution of a hyolingual MAP involved with rhythmic intra-oral food processing, or chewing, in gnathostomes. Chewing is likely a basal gnathostome trait, retained in many members of most major lineages. EMGs were recorded from evolutionarily homologous muscles driving anteroposterior hyoid ‘tongue’ movement and dorsoventral mandibular ‘jaw’ movement. In a ‘shallow’ comparison of sarcopterygians, cross-correlation analyses were used to scan for MAP reorganizations coinciding with changes in physiological ecology. In a ‘deep’ comparison between osteichthyans and sarcopterygians, time-series analyses of EMG indicate that major morphological change, involving hyoid skeleton reduction and appearance of new hyoid muscles, is accompanied by MAP changes that fundamentally reorganize the hyolingual kinematics of chewing.